Jason, curious if you ever mixed up my soup recipe for the APHS?
This was a later recipe than I may have sent you a year or so ago.
The cost difference is pretty drastic once you leave the Arista film.
I tried your pyro-based soup and really wasn't too happy with the results, but I missed the Rodinal-based one. I will give it a try, as I am really looking to stay on the cheap right now. I don't have any Rodinal around, (can you believe I have never used it?) but will see if I can find some nearby.
Originally Posted by Donald Miller
Several of us are reasoning based on the spectral response of the two film types. You haven't addressed this reasoning, except with the unconvincing sweeping generalization that "you can not make something simply by removing somenthing else".
Someone just gave me a 25 sheet pack of Kodak 4125 - I was wondering if it could be used as...I think I just figured out what the 'in camera film' statement meant..I don't have any need to copy like it was originally intended for, but want to use it as 'ortho' film in film holders in a camera.
Does anyone have any idea what ISO to use outdoors with 4125? Let's ignore the out-of-date factor - I can deal with that later if necesssary - I just want to get in the ballpark.
I also got a box of 8x10 'high definition x-ray imaging film', which is apparently a single emulsion, ortho film. I don't know if it's true 8x10 or fits our kind of filmholders - I tossed it in the refrigerator as soon as it arrived.
It's private labeled. I found out who made it and have been bugging both companies for misuse and abuse info...they don't seem to know how to answer spectral and resolution questions. What constitutes 'high definition' in x-ray work doesn't seem to mean anything to anyone I've asked yet...other than the suggestion that single emulsion has higher definition than double emulsion.
BTW, someone told me household bleach can be used to remove emulsion from one side, but I think that exceeds even MY limits for impracticality.
I hope this next question fits with this thread...I'm thinking if I can find my Minor White et al Zone System book, there was a discussion of controlled exposure testing - but lacking it in-hand at the moment, I'll ask.
Is there a better 'plan' to figure out how to misuse mystery film, outdated film etc., than to just meter an 18% gray card and open a dark slide a fraction of a sheet at a time for increasingly longer exposures, say 1/8 sheet @ t seconds, 1/4 sheet at 2 x t seconds, 3/8 sheet at 3 x t seconds and so on?
Someone suggested to me defocussing the lens after 'composing' on the gray card to avoid distraction by the texture...I didn't understand the benefit of that.
Even though the Kodak 4125 is discontinued, the datasheet is still available: http://www.kodak.com/global/en/profe.../f17/f17.jhtml
" KODAK Professional Copy Film is an orthochromatic film (sensitive to blue and green light and ultraviolet radiation) designed for copying continuous-tone originals. .....
This special-purpose film works differently than other black-and-white films. Generally, the contrast of negatives is controlled by development. However, with this film, contrast in the copy negative is controlled by both exposure and development. "
What the don't mention in words -- the characteristic curves show the film to be a direct reversal film -- more exposure gives less density.
The tungsten speed is listed as ISO 10. The daylight speed must be faster since daylight has much more blue light than tungsten, but exactly how much is tricky to say since exposure also controls contrast.
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Interesting - direct reversal...copy film...makes sense...
I guess I'll just give it a try.
Look at the curves again. It is definitely not a direct reversal film. I have some and use it for internegatives. The curve posted shows reflection density against transmission density on the film negative. IOW, it shows a curve for copying positives, not negatives. Kodak did have a direct reversal film named SO-132, but has been gone for a long time.
Originally Posted by Donald Miller
By using a minus red filter only the short wave lengths of the visible spectrum, the blue and green portions, will reach the film. Those colors will appear lighter while the other colors of the spectrum, the longer wavelength yellows and, oranges will appear darker with red showing as black. Of course, how well this works depends on how good the filter is in cutting off the longer wavelengths. No filter is perfect but this should produce a very good approximation of the ortho look.
My reponse was directed to someone who contended that the converse of what you stated was possible.
Originally Posted by Gerald Koch
My position is that one can not filter and duplicate a true panchromatic material from an orthochromatic material. A great deal depends on the spectral characteristics of the emulsion.
Orthochromatic materials are sensitive to the blue spectrum and may have very little if any sensitivity to red. So therefore by shutting of the blue spectrum with a minus blue filter does not necessarily equate to making an orthochromatic material into a panchormatic material. If the sensitivity to the red spectrum is not present as a characteristic of the emulsion, no amount of filtering, regardless of the filter used is going to create emulsion sensitivity that does not exist.
Thus I stand with my earlier position that removal of something does not equate to the creation or the addition of something that is not present as an emulsion characteristic.
As we both know, panchromatic emulsions have a more global sensitivity then orthochromatic materials. As I stated originally that was not what I was addressing. My original statement addressed the mistaken belief that one could filter orthochromatic materials and have them replicate a panchromatic emulsion. Since orthochromatic materials have a limited spectral response, there is no amount of filtering that will effect a spectral change to the extent that they replicate panchromatic materials.
For those that may be interested, I direct them to the chart of spectral response found it Adams "The Negative" This chart may be found on page 22.